Overview Handwashing with soap is a simple yet vital tool to prevent disease transmission, particularly in school environments. Research indicates that handwashing interventions in low- and middle-income countries can reduce acute respiratory infections by an average of 17% and decrease diarrheal infections by 30% in childcare settings. Despite this, global estimates show that only 19% of people wash their hands with soap after using the toilet. In Sri Lanka, the National Water Supply and Drainage Board—with support from ADB’s technical assistance—pilot-tested the use of environmental “nudges” to increase handwashing with soap among students in five primary schools. Unlike traditional approaches that educate or motivate students to wash their hands, nudges aim to change behavior by modifying the environmental context. This involves using environmental cues that engage automatic decision-making processes, which are quick and unconscious. The project’s primary objective was to evaluate the effectiveness of the nudge approach within the Sri Lankan school context to gain and build practical experience in implementing this method. Challenge Despite the availability of functioning handwashing facilities, initial studies showed that only 15% of students in the selected primary schools washed their hands with soap after using the toilet. The low compliance rate in schools was concerning because children are more susceptible to illnesses due to inadequate sanitation and hygiene practices. The challenge was to find a way to effectively and sustainably encourage children to change their handwashing behavior. Encouraging the simple behavior of handwashing with soap is not just a public health win—it also makes economic sense, reducing healthcare costs, and absenteeism among students. Solution Handwashing with soap is one of the most effective and affordable ways to combat the spread of infectious diseases and improve student attendance in schools. An estimated investment of $3.35 in handwashing promotion to bring health benefits is similar to an $11 investment in latrine construction, $200 investment in household water supply, and an investment of many thousands of dollars in immunizations. The National Water Supply and Drainage Board–ADB pilot project used environmental nudges as subtle interventions to influence behavior by changing the environment around the students. Such nudges were new to the Sri Lankan context but had previously been piloted with promising results in Bangladesh and the Philippines, among other countries. The five schools[1]selected for participation in Sri Lanka's handwashing nudges project had to have functional toilets and access to water for handwashing as minimum requirements. The pilot involved 1,766 students from low-income disadvantaged communities across urban, peri-urban, and rural areas. The nudges were designed using the easy-attractive-social-timely framework, which encourages the adoption of target behaviors by making them easier, more attractive, and engaging. Some of the handwashing nudges included: Colorful paths and footprints leading from the toilets to the handwashing stations, making the route to wash hands attention-grabbing and visually appealing. Bright handprints painted on the walls above the handwashing station, cueing students to wash their hands. Mirrors installed above the sinks which attract students to the handwashing area by leveraging natural "mirror-checking behavior". A handwashing facility with a nudge was installed at a central location between school buildings and on a path that students take to return to their classrooms. Photo credit: ADB. The interventions aimed to make handwashing not only easier but also encouraged students to wash their hands without requiring extensive instruction or reminders. Representatives from local authorities, zonal offices of education, and school communities were involved in the project—from nudge design to impact measurement. Principals, teachers, representatives of the School Development Society, and National Water Supply and Drainage Board staff designed and adapted the nudges based on the sanitation and hygiene facility of each school. Results The impact of the nudges was measured through observations of student handwashing behavior at three key points: at the start of the project, one week after installation of the nudges, and six weeks after installation. Over 1,500 observations were made at each time point. The results showed a dramatic change in student behavior (Figure 1). Within one week of installation, handwashing with soap rose to 61% from 15%. However, this impact tapered off to 47% between weeks one and six, likely due to a two-week vacation that interrupted habit formation. Figure 1: Observed Handwashing at Nudge Pilot Schools, Percent of Students The nudges increased handwashing among both girls and boys, with a greater increase observed among girls (52 versus 41 percentage points). The reasons behind this difference remain unclear and warrant further investigation. Beyond improving handwashing rates, the cheerful changes to the school sanitation areas positively shifted attitudes towards these facilities among students, school management, and parents. One principal noted that the new colorful handwashing area transformed the school toilets from something preferably hidden to a positive feature of the school. The success of school handwashing nudges in Sri Lanka has generated strong interest in scaling this approach nationwide. Lessons The pilot provided proof of concept for school handwashing nudges in Sri Lanka. It demonstrated that nudges can significantly increase handwashing rates, even without behavior change communication. A future scale-up of the pilot should explore whether adding nudge elements (e.g., painted “observing eyes” above the handwash area) could help reduce the impact difference between boys and girls. Handwashing nudges must be adapted to the context of each school. The number, design, and placement of facilities vary greatly, making a one-size-fits-all approach impractical. Involving local stakeholders in the design process helps optimize this adaptation. The timing of nudge installation is crucial to allow sufficient time for habits to take root. Research shows that habit formation can take from a few weeks to several months, depending on the behavior's complexity and the individual's context. The project showed that three weeks were insufficient for some students to acquire a sustained habit, highlighting the need for extended periods to reinforce new handwashing with soap behaviors. Repeated exposure to the nudges and longer sustained practice of handwashing may help solidify these behaviors into lasting habits. Behavioral "nudges" should be a key tool for policymakers and program designers. Evidence from Sri Lanka demonstrates that nudges have the potential to drastically improve handwashing with soap in schools. They also require little to no additional time from teachers, unlike traditional hygiene-education methods, which often demand significant human resources to be effective. Moving forward, collaboration across sectors will be essential to ensure the effective implementation and expansion of this strategy, driving improvements in both public health and education outcomes. The pilot demonstrated the effectiveness of nudges to significantly increase student handwashing rates, contributing to public health in schools and their communities. By fostering these habits in educational settings, this can instill lifelong health practices and create healthier communities. A video of this initiative can be found here. [1] The five primary schools in the pilot projects are Baptist Primary School, Biyagama; Dharmadassi Primary School, Biyagama; Kudabuthgamuwa Primary School, Kolonnawa; Wellampitya Primary School, Kolonnawa (Western Province); and Kirindagama Primary School, Kirinda (Southern Province). Resources D. Walker, R. Hutubessy, and P. Beutels. 2010. WHO Guide for Standardisation of Economic Evaluations of Immunizations Programmes. Vaccine. 28 (11). pp. 2,356–9. G. Hollands, et al. 2013. Altering Micro-Environments to Change Population Health Behaviour: Towards an Evidence Base for Choice Architecture Interventions. BMC Public Health. 13. pp. 1218. R. Dreibelbis, et al. 2016. Behavior Change Without Behavior Change Communication: Nudging Handwashing Among Primary School Students in Bangladesh. International Journal of Environmental Research and Public Health. 13 (1). pp. 129. UNICEF. 2021. Sri Lanka Hand Hygiene Snapshot. Ask the Experts Pedro Miguel Pauleta De Almeida Senior Urban Development Specialist, Water and Urban Development Sector Office, Sectors Group, Asian Development Bank Pedro Almeida has over 25 years of experience in engineering, management, evaluation, and technical monitoring of complex infrastructure projects. With ADB, he has worked in Bangladesh, Sri Lanka, Nepal, and India. Before ADB, he was a consultant in the Kyrgyz Republic. In Brazil, he managed World Bank-funded initiatives and infrastructure projects. He also served as a site manager in Portugal and Mozambique. Pedro holds a degree in Civil Engineering, an MSc in Buildings, and a postgraduate degree in Health and Safety in construction. Follow Pedro Miguel Pauleta De Almeida on Lene Gerwel-Jensen Behavior Change Specialist / WASH Specialist Lene Gerwel-Jensen specializes in the fields of social and behavior change and water, sanitation, and hygiene (WASH). She has more than 20 years of experience working and consulting for governments and international organizations in the development and humanitarian sectors. In this capacity, she has led and contributed to the design, implementation, and evaluation of WASH and behavior change interventions across Asia, Africa, and Latin America. She has a background in public health and communication. Follow Lene Gerwel-Jensen on Christian Walder Water Sector Engineer, European Investment Bank Christian Walder is responsible for the assessment of the technical, operational, and environmental viability of capital investment projects and programs in the field of water and wastewater services, storm water management, and flood protection. He is an environmental engineer by training and has extensive experience in the preparation and implementation of sustainable and inclusive water projects in numerous countries across Asia, the Pacific, Europe, and Africa. Follow Christian Walder on Marie Christelle Garcia Strategic Knowledge Management & Communications Specialist, Asian Development Bank Marie Garcia is a development communications professional supporting knowledge and outreach initiatives. A writer and storyteller, she creates content across different platforms, including publications, blogs, social media, and other knowledge products. She specializes in communications for climate change, water, and urban development. She holds a master's degree in Nonfiction Writing from Sarah Lawrence College in New York. Follow Marie Christelle Garcia on Asian Development Bank (ADB) The Asian Development Bank is committed to achieving a prosperous, inclusive, resilient, and sustainable Asia and the Pacific, while sustaining its efforts to eradicate extreme poverty. Established in 1966, it is owned by 69 members—49 from the region. Its main instruments for helping its developing member countries are policy dialogue, loans, equity investments, guarantees, grants, and technical assistance. Follow Asian Development Bank (ADB) on Leave your question or comment in the section below: View the discussion thread.